freaked out after brothers illness

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Kiki is acting very strange with her brother lately...
His name is Winter and he is recovering from a urinary blockage. He has been secluded to our bedroom for a week while recovering so we can keep a close eye on him. The last couple days though we have decided to let him come out in the day time so he can resume his normal life.
Kiki wont let him him go anywhere near her. Any time he even so much as walks by her she slaps him and hisses like crazy. am just wondering if anybody knows why this might be and what I could do to help?
Thank you in advance

He may smell different to Kiki because he was in the bedroom, or have some sort of smell from the infection or medication given to him. What I had read other CATSTER members suggesting is to take an old towel or t-shirt and first rub Kiki with it and then rub her brother with the same towel or t-shirt. This usuall seems to calm the "Scary Cat".

Hmmm, I wonder if it's the smell from being at the vet, or like someone else suggested, the medicine, or he smells different, from being sick? Hopefully it will pass. Some people swear by feliway for things like this, like the plug in or the room spray, but I have it and have never found it to help, and it's a little expensive. Maybe you will just have to keep them separated when you are not able to watch them, until Winter is feeling completely back to normal? I hope it gets better soon.

Yea, we are definitely keeping and eye on them, and when we leave Winter just goes back in his bedroom, so they are not alone together, she is getting a bit better so hopefully it will get back to normal soon, thanks Beep